Why smoking pot makes food taste so delicious

Sure, a few minutes ago you might have said you were too full to eat another bite, but a few drags from a joint later and those gooey bites of salty goodness are hitting the spot like no other snack has before.

Marijuana may effectively flip a circuit in the brain that is normally responsible for quelling the appetite, triggering us to eat instead, according to a new study in mice published in the journal Nature Neuroscience.

It all comes down to a special group of cells in the brain which normally get activated, or switched on, after we've eaten a big meal to tell us we've had enough. In the brain, though, the psychoactive ingredient in weed appears to activate just one component of those appetite-suppressing cells, known as pro-opiomelanocortin (POMC) neurons, making us hungry instead.

"Imagine getting in a car and having the brake pedal suddenly become the accelerator. That's effectively what's happening," Yale University School of Medicine professor of neurobiology Tamas Horvath, one of the study authors, told Business Insider.

In their experiments with mice, the researchers found that the animals injected with tetrahydrocannabinol (or THC, weed's main psychoactive ingredient) had higher numbers of active, or "switched on," POMC neurons. You might be thinking, more appetite-suppressing cells, less appetite, right? Wrong. And that's where the findings get interesting.

To find out what was going on, the researchers took a look at the genes that produce these cells, called Pomc (no caps) genes. As it turns out, the genes that produce these cells also churn out two separate proteins — one that tells us that we're full and another that stimulates our appetite.

The THC, the researchers found, effectively turns on the appetite-stimulating protein but has no effect on the appetite-suppressing one.

The new study was in mice, and it's possible that this mechanism works differently in humans. But years of research have linked smoking or ingesting weed with eating more, and several studies have documented the role POMC cells play in making us feel full.

A study from way back in 1976, for example, found that both heavy and casual smokers ate significantly more food — and gained an average of three pounds more than non-smokers — just within the first five days of the trial period. Similarly, a 2011 study found that in mice, activated POMC cells appear to block eating.

But this most recent paper is the first to give researchers a closer look into how the cells that influence our appetites actually work.